I have been looking for a (free) simple timer for Mac for years and years. My workload is so immense and scattered, with so many clients, it is best approached in hour-long chunks. Many lackluster products have come and gone from my desktop. This ap's combination of fun graphics and the feature that allows various behaviors when the time is up--notably starting or stopping iTunes--has made it a surprise champion among the other underachieving products in my personal timer championship. If they were to improve it, I'd suggest making it possible to set a time (30 minutes) without clicking 30 times.
That said, this product's minimal features are a bit of a virtue. I don't waste too much time trying to fine-tune the preferences, as it has only three.